The present invention is in the field of optical interconnection devices, such as those that may be useful in routing information for communications systems.
This invention relates to apparatus supporting optical interconnection, such as those that may be useful in the routing of signals in the communications industry. In communications systems such as telecommunications systems, optical signals currently must be down-converted to an electrical signal before being switched. The bandwidth of these electrical signals is much lower than that of optical signals. This conversion is a barrier to a fast Internet system capable of delivering applications requiring significant bandwidth, such as streaming on-demand video and music. It is therefore desirable to use a system that keeps signals in their optical form without having to convert to a slower, less-efficient electrical system.
One area to be addressed is the electronic switches in fiber-optic backbones. Backbones are expensive communications links between major cities. Optical fibers often carry information to central hubs in these major cities, then creating a bottleneck at each hub while all this information waits to be converted into electrons and switched by bulky electronic switches. Because each fiber carries multiple signals on different wavelengths, the signals must be optically separated before each one can be down-converted and electronically switched.
Because of this, the industry has turned its attention toward photonic switches. Photonic switches do not require signal down-conversions, and are capable of optically directing even complex light streams. Several variations of these photonic switches have been reported. Agilent reportedly uses bubbles to deflect light between crisscrossing glass columns in order to direct light from one switch to the next or back and forth among the switches to get to the various outputs. Coming is reportedly investigating liquid crystals to redirect the light streams. Bell Labs is reportedly using tiny micro-mirrors to direct beams to the appropriate fibers. While these systems are much smaller that the previous switching systems, and may effectively achieve the desired optical switching, they can be very complex. For example, in the Bell Labs device where an array of micromirrors is used to direct beams to the appropriate fiber, each mirror must be accurately calibrated to send a beam to any of the appropriate fibers. The calibration must also take into account any minute variation in position from fiber to fiber, an array of fibers not being aligned in perfect rows and columns.
In earlier optical interconnection devices, such as those described in U.S. Pat. No. 6,266,176, the number of possible outputs to which a given input could be switched was related to the number of bounces, m, a beam made in a White cell raised to some power (m1, m2, etc.). In the present invention, we present a binary switch, in which the number of outputs is proportional to 2m, which will in general be a much larger number. We also describe a family, of higher order interconnection devices, in which the number of outputs is proportional to 3m, 4m, etc. Thus, for a given number of bounces, each input can be switched to a larger number of outputs than earlier designs.
It is therefore an object of the current invention to create a photonic switching system that is compact in design, relatively simple to setup and operate, and can effectively route multiple complex light streams.
Although described with respect to the field of communications, it will be appreciated that similar advantages of optical routing, as well as other advantages, may be obtained in other applications of the present invention. Such advantages may become apparent to one of ordinary skill in the art in light of the present disclosure or through practice of the invention.
The present invention presents a dual-White cell approach for creating the multiple bounces, but it will be recognized that other methods of producing multiple bounces exist (as described in U.S. Pat. No. 6,266,176 and in pending application Ser. No. 09/688,478, each incorporated herein by reference). Also presented are designs based on a liquid-crystal spatial light modulator, but it will be shown that other spatial light modulators, including micro-electro-mechanical machine (MEM) devices such as a digital micro-mirror device, can be used instead. Adapting the dual-White cell to MEM""s has been discussed in U.S. Pat. No. 6,266,176 as well.
An optical interconnection device of the present invention includes at least one input light source for generating at least one individual light beam. Each individual light beam emerges from its respective input light source and enters a first optical configuration. The first optical configuration is adapted to receive each individual light beam and to direct each individual light beam to a spatial light modulator. The first optical configuration comprises a plurality of optical elements configured so as to define a plurality of possible light paths for each individual light beam. After being directed to the spatial light modulator, an individual light beam may be directed to a second optical configuration. The second optical configuration is adapted to receive the individual light beams reflected from the spatial light modulator. The second optical configuration comprises at least one spot displacement device.
In a preferred device of the present invention, each light beam is introduced by an input light source. Each light beam is received by the first optical configuration before being directed to a spatial light modulator. The spatial light modulator may reflect each light beam either back to the first optical configuration or to a second optical configuration. A light beam reflected to the second optical configuration may encounter a spot displacement device. Eventually each light beam is directed to a receiving device adapted to receive light beams exiting the optical interconnection device. The optical interconnection device is therefore capable of providing a multitude of outputs for a given input.
In a second embodiment of the present invention, the first optical configuration may additionally comprise at least one spot displacement device.
Irrespective of embodiment, it is preferred that the first optical configuration comprises a first plurality of optical elements comprising mirrors, lenses, gratings, and prisms. It is further preferred that the second optical configuration comprises a second plurality of optical elements comprising mirrors, lenses, gratings, and prisms.
It is also preferred that each spot displacement device comprise at least one column, each spot displacement device being capable of shifting a given light beam by at least one row on the spot displacement device thereby causing the returning light beam to be shifted on the spatial light modulator. It is most preferred that each additional column of the spot displacement device displace the light beam by twice (or more) the displacement of the previous column. For example, the first column would displace a light beam by one, the second column would displace a light beam by two, the third column would displace a light beam by four, etc.
It is also preferred that each spatial light modulator be selected from the group consisting of liquid crystal spatial light modulators, two-state micro-electro-mechanical devices, and three-or-more-state micro-electro-mechanical devices.
In yet another preferred embodiment of the present invention, at least one input light source introduces at least one individual light beam into a first optical configuration. The first optical configuration comprises a plurality of optical elements configured so as to define a plurality of possible light paths and at least one spot displacement device. A given light beam may pass to the spatial light modulator before entering a second optical configuration. The second optical configuration comprises a plurality of optical elements configured so as to define a plurality of possible light paths. The spatial light modulator comprises at least one column, and each column comprises at least two rows. The spatial light modulator is adapted to select a light path from among the possible light paths for a given light beam and to direct the light beam to the selected path. The spot displacement device is capable of shifting a given light beam on said spatial light modulator by at least one row. A plurality of output positions are available to receive a given light beam, thereby removing the light beam from the optical interconnection device.
In a preferred embodiment of the present invention, the time it takes a given light beam to traverse the optical interconnection device is the same as all other light beams. Further, in preferred optical interconnection device, a given light beam may be directed to a given output position by either the first optical configuration, the second optical configuration, or by the spatial light modulator. A preferred device may additionally comprise at least one spot displacement device in the second optical configuration. Additionally, it is preferred that the first plurality of optical elements comprise optical elements selected from the group consisting of mirrors, lenses, gratings, and prisms. It is further preferred that the second plurality of optical elements comprise optical elements selected from the group consisting of mirrors, lenses, gratings, and prisms.
In a preferred optical interconnection device of the present invention the spot displacement device comprises at least one column, each spot displacement device being capable of shifting a given light beam by at least one row on said spot displacement device and thus on the spatial light modulator. It is most preferred that each additional column on the spot displacement device is capable of displacing the light beam by twice (or more) the displacement of the previous column.
It is also preferred that each spatial light modulator be selected from the group consisting of liquid crystal spatial light modulators, two-state micro-electro-mechanical devices, and three-state micro-electro-mechanical devices.
The present invention also provides a spot displacement device, comprising at least one column. The spot displacement device shifts a light beam by at least one row on the spot displacement device. Each additional column of the spot displacement device is capable of displacing a light beam by twice (or more) the displacement of the previous column.